Projectile



Sept. 5, 1961 D. T. M RoBERTs 2,998,779

PROJECTILE Filed July 10, 1944 l I? I5 [2' INVENTOR DONALD 7: MAOROBERTS BY 4 '5 a ATT EY United States Patent 2,998,779 PROJECTILE Donald T. MacRoberts, Shreveport, La., assignor to the United States of America as represented by the Secretary of the Navy Filed July 10, 1944, Ser. No. 544,195 1 Claim. ('Cl. 102-93) This invention relates to projectiles for guns and more particularly to a novel sub-caliber sabot-projectile adapted to attain high velocities when fired from a gun.

One object of my invention is the provision of a subcaliber projectile having an ogival nose and a detachable bourrelet mounted on the ogive and adapted to move rearwardly thereon and expand radially when the projectile is fired from the gun, in order to provide a tight fit in the gun barrel.

Another object of the invention is to provide a subcaliber sabot-projectile having an ogival nose and a hourrelet mounted on the ogive portion so as to be maintained in spaced relationship with the sabot, which is mounted on the rear portion of the projectile, thus insuring a well centered fit of the projectile during its travel through the gun bore.

A further object of my invention is to provide a projectile as described above which is simple to manufacture and adapted for large quantity production.

These and other objects of the invention will be apparent from the following specification and the accompanying drawing, in which FIG. 1 is a side elevation of a projectile made in accordance with my invention, showing the projectile in a gun barrel prior to radial expansion of the bourrelet;

FIG. 2 is a longitudinal sectional view of the projectile in the gun barrel after radial expansion of the bourrelet, and

FIGS. 3, 4 and are cross sectional views taken on lines 3--3, 4-4 and 55, respectively, of FIG. 2.

In the drawing, the numeral represents the barrel of a gun adapted to fire a sub-caliber sabot-projectile comprising a core 11. On the rear end portion of the core is a sleeve 12, made of plastic or other light-weight material, which may be press-fitted on the core. As shown, the sleeve 12 is weakened by longitudinal cuts 12a radiating from the inner surface of the sleeve and terminating short of its outer surface. Mounted onthe core 11 in front of sleeve 12 is a sabot 13 in the form of a ring completely segmented into three or more segments which fit into an annular groove 13a in the core near its rear end, the sabot segments 13 being held in place by a turning band 14 extending around the sabot. The turning band 14, which may be made of copper, is pressfitted, shrunk or otherwise secured on the sabot 13 and has tongues 14a disposed in annular grooves in the sabot.

The nose portion of the projectile core is ogival or tapered in configuration, as shown at 11a, and carries a cylindrical bourrelet 15 made of plastic or other light weight material and partially segmented into three or more segments by longitudinal radial cuts 15a. In some cases, it may be necessary to provide means, such as a pin or a ridge (not shown), forward of the bourrelet in order to prevent its sliding off the nose of the projectile. The inner surface 15b of the bourrelet is frusto-conical and fits closely around the tapered portion 11a of the projectile core, while the outer surface of the bourrelet is cylindrical.

When the projectile is fired from a gun, the setback force due to the sudden acceleration of the projectile moves the bourrelet 15 slightly rearwardly on the nose portion of the projectile and thus causes the bourrelet to expand slightly, by the action of the tapered portion 11a on the bourrelet surface 15b. As a result, the outer cylindrical surface of the bourrelet is pressed against the wall of the gun bore to provide a tight fit (FIG. 2) and better centering and support of the projectile in the gun bore. When the projectile leaves the muzzle of the gun, the sabot, turning band, sleeve and bourrelet break apart and release from the core 11 under the centrifugal force generated by their high speed rotation, it being understood that the turning band 14 is engraved by the usual rifling (not shown) in the gun barrel 10 to cause the rotation. The projectile core 11 is thus free to continue towards the target at a high velocity without the aerodynamic drag which would otherwise be imposed upon it by the released parts. Since the bourrelet is retained on the forward portion of the projectile core and is not allowed to move rearwardly into contact with the sabot, two separate and spaced centering means are provided which increase the stability of the projectile in the gun bore and thereby increase its flight stability. In this connection, it will be understood that the rearward movement of the bourrelet on core 11 is limited by the wall of the gun bore, more specifically by the usual rifling (not shown). That is, when the bourrelet has undergone the maximum radial expansion permitted by the wall of the gun bore, further rearward movement of the bourrelet on the core is positively prevented by the tapered nose portion 11a of the core, as shown in FIG. 2.

The new projectile is of simple construction, and its relatively few parts may be manufactured at low cost and easily assembledi The bourrelet 15 and sleeve 12 are so designed, as by means of the radial cuts 15a and 12a, respectively, that their strengths are substantiallyexceeded by the centrifugal stresses to which they are subjected when the projectile emerges from the gun muzzle, whereby their release is eifected with an ample margin of certainty. Similarly, the turning band 14 is designed to break readily under the centrifugal force when it emerges from the gun muzzle and is no longer constricted, whereby .the sabot segments 13 are released from the groove 13a. The bourrelet 15 is made of a suitable material capable of expanding, as described, Without fracturing prior to its release from the gun muzzle.

With the construction described, the parts of the projectile mounted on the core 11 are released quickly and positively after the projectile passes through the gun bore, with a relatively small energy loss and without substantial effect upon the flight of the core. Since the ogive portion of the core 11a is utilized to expand the bourrelet against the inner wall of the gun barrel and, in conjunction therewith, to limit rearward movement of the bourrelet, it is unnecessary to provide separate means for looking the bourrelet in a fixed axial position on the core or to proportion the external diameter of the bourrelet accurately. Accordingly, the construction of the projectile is simplified.

I claim:

A subcaliber projectile comprising a subcaliber cylindrical core having an ogival nose portion and an annular groove adjacent to its base, a pair of sleeves carried by the core and constituting a twin bourrelet to ride the lands of a rifled gun bore, one of the sleeves being mounted on the rear of the core in'back of the groove,'the other sleeve being mounted on the'ogival nose, a sabot fitted in the groove and being abutted by the rear sleeve, and a turning band atfixed annularly of the sabot, being diametrally larger than the sleeve to be engraved by the grooves of the rifling.

References Cited in the file of this patent UNITED STATES PATENTS 5 Rollins Jan. 28, 1862 Turechek Mar. 9, 1943 4 FOREIGN PATENTS Great Britain Jan. '18, 1917 Great Britain Aug. 21, 1919 Sweden Nov. 5, 1919 France Apr. 23, 1935 France Dec. 19, 1936 

